Empty schema {} causes validation failure

[ra-one]

There are multiple schemas which contains {} causing validation to fail.
https://github.com/singer-io/getting-started/blob/master/docs/BEST_PRACTICES.md#schemas

For examples, orders.json and definitions.json

[sphinks]

As there is no recent merges and lot of PRs are just stuck - it looks like there is nobody who maintain the repo. To get an idea how to fix the issue take a look into my PR: #83 and perfrom the same with you schema to let the tap working as expected.